To conveniently support an electrical wiring device, such as a switch or a receptacle, an electrical lighting fixture, or simply a cover plate, an electrical outlet, or wiring, box is mounted in an opening made in a wall or ceiling and the electrical apparatus or cover plate is fastened to the box by means of two mounting screws. Conventional electrical outlet boxes are stamped from metal and typically have threaded earholes at the top and bottom for receiving and threadedly engaging the mounting screws. More recently, these boxes are made from nonmetallic materials, such as thermoplastic compositions, and various spring clips or other extra inserts are used to fasten the mounting screws to the electrical box as the screw passes through a bore formed in each of the box bosses. The longitudinal axis of the bore is substantially perpendicular to the face of the boss. Such bosses include an internal bore which cooperates with the structure of the clip to mount the clip fixedly in the boss.
However, the spring clips used for holding mounting screws in nonmetallic boxes have serious disadvantages. For example, the use of clips presents additional inventory which must be accounted for and ultimately increases the cost of manufacturing the electrical box as well as the chance of losing a necessary part. Moreover, the integral bosses sometimes do not adequately hold the mounting screw to the box, and in other cases, the clips may break under screw loading. In addition, these prior art clips do not significantly serve to angularly align the screw with the mounting bore. Thus, the screw may not easily thread straight into the mounting bore when it is rotated. The screwdriver can slide out of the slot in the screw head because there is no means for holding the screw firmly and therefore, it is free to move from side to side.
Examples of these prior art devices regarding outlet boxes as well as other screw retaining assemblies are disclosed in the following U.S. Pats. U.S. Pat. No. Re. 29,752 to Jaconette, Jr.; U.S. Pat. No. 3,263,949 to Conrad; U.S. Pat. No. 3,876,821 to Pringle; U.S. Pat. No. 3,967,049 to Brandt; U.S. Pat. No. 4,025,144 to Thibeault; U.S. Pat. No. 4,130,335 to Kinney; U.S. Pat. No. 4,295,003 to Borja et al; and U.S. Pat. No. 4,355,198 to Gartland, Jr.
Accordingly, there is a continuing need for improvement in rapidly, easily and economically mounting various types of electrical devices or covers to nonmetallic outlet boxes.